There is conventionally known an image reading apparatus for reading a document, configured to perform different image processing based on image data corresponding to a read image to generate a plurality of different image data. For example, US Application Publication No. 2006/0221415A1 discloses a color copier that executes, as image processing, color image data generation processing and monochrome image data generation processing and executes, in parallel with determination processing of determining whether an input image is a color image or a monochrome image, and then quickly transfers to an external device one of the color and monochrome image data in accordance with a result of the determination.